In the area of automation technology what are known as Programmable Logic Controllers or a PC-technology-based emulation of said controllers are used to execute control programs for a technical installation. These control programs generally comprise a number of software modules, for example for implementing specific control tasks using a closed-loop controller, with the software modules in their turn mostly being subdivided into further software modules such as organizational components, function components, data components or step components for example.
The term “software program” used in this document is thus intended to include both a complete software program as a whole and also individual software modules of a more complex software program as well as further software modules, possibly as part of a software module (such as the previously-mentioned components for example).
Thus input signals in the sense of the present invention are both those signals occurring as a result of direct measurements by means of sensors and to be transmitted to the software program and also those signals which are generated by a software program in the above sense as output signals and are transferred to a downstream software program for further processing as its input signal or input signals.
A signal source can thus be both a sensor which detects original signals occurring, but also an intermediate result of signal processing, which is determined for example by a software program and/or software module and/or further software module, and transmitted to a further software program and/or software module and/or further software module.
When signals occur in a signal source the generated signal can be incorrect, bad (noisy) or sometimes not available, as a result of a signal source fault for example. For example, as a result of a wire break at a sensor, the signal detected by the sensor cannot be forwarded or can only be forwarded intermittently, or a division by zero is performed in a calculation algorithm in signal processing in a software program and/or software module and/or further software module.
To enable these types of disturbed signals to be recognized, the process of providing a marking (a so-called quality code for example) along with the signal to indicate the quality of the signal is known. A quality code of “bad” would then mean that on further processing of such a signal by software programs located downstream in the signal direction it is possible to take into account these types of errors by enabling a warning message to be generated for example which points to the bad signal or even by suppressing further processing.
It is further known that the marking of a bad signal is dominantly inherited, meaning that those software programs which process a bad signal also mark their relevant output signals as bad.
If these types of bad signal are now fed back in a type of feedback loop as input signals to software programs and/or software modules and/or further software modules, as a result of the dominantly inherited marking “bad”, each of the output signals which is included in the feedback loop remains in the “bad” state although the faults in the signal source can have been rectified in the meantime.